Vocal learning
The neural circuitry involved in the production of contact calls (left), begging calls (middle) and subsong to adult song (right) in chipping sparrows.
Definition
„Vocal learning, as we discuss it here, refers only to learning sounds, that is, to instances where the vocalizations themselves are modified in form as a result of experience with those of other individuals“ (Janik 1997, 59)
Vocal Learning is not synonymous to:
- auditory learning, but auditory learning is a condition for vocal learning
- contextual learning, e.g., learning how and when to use specific sounds
- speech, but it is a precondition for speech
Degrees of Vocal Learning
- control over the duration and amplitude of a call
- control over frequency features
- ability to imitate completely new sounds / vocalizations
(Janik 1997, 60, 71, 75, 86)
Possible evolutionary forces for the evolution of vocal learning in mammals
- Intersexual Selection
- Intrasexual Selection and Resource Defense
- Individual Recognition
- Familial or Group Recognition
- Population Identity
- Intense Speciation
- Habitat Matching
> 5.-7. are rather unlikely (Janik 1997)
A common factor among vocal learning species is their high mobility three-dimensional space (Janik 1997, 87). In humans, language possibly developed in gestures first. When Vocal Learning evolved after that it was a great advantage to use vocalizations instead of gestures so that Vocal Learning could persist (Janik 1997, 88).
Motor Theory of the Origin of Vocal Learning
Caused by mutation, the pathway for Vocal Learning developed out of a pre-existing non-vocal motor pathway. (Jarvis 2007, S42)
Genetics
The only gene discovered so far which has clear links to vocal learning is Fox-P2. It belongs to a large transcription factor gene family and acts as a suppressor of transcription.
“FoxP2 may be important for establishing and maintaining brain pathways including, but not limited to, those essential for learned vocal communication” (Haesler et al. 2004, 3174)
References
- For more information on references see this article's Bibliography.